The present invention relates generally to pellet marking devices, and in particular, to a pellet marking device which makes use of an ink-jet system.
A variety of devices have been developed for applying desired indicia to pellet-shaped articles, including both regularly and irregularly shaped pellets. For example, U.S. Pat. No. 4,632,028; 4,500,012; 4,413,556; 4,394,933; 4,377,971; and 4,369,702 address various devices which may be used in applying indicia to articles such as candies, pharmaceutical capsules, tablets and the like, or any other pellet-shaped article to which identifying indicia are to be applied.
In terms of the means which are used to actually apply the indicia to these various articles, each of these devices, and the devices of the prior art, have conventionally made use of a contact-type printing system. To this end, a pair of rollers are provided including a design roll which forms the indicia to be applied to the articles, and which is disposed within an appropriate supply of ink, and a printing roll which is in contact with both the design roll and the articles which are to receive the indicia, for transferring the ink-laden indicia from the design roll to the articles in question. An exemplary description of such a device may be found in U.S. Pat. No. 4,528,904.
Each of the above-described pellet marking devices is therefore based upon a printing technique which requires direct contact between the printing assembly and the articles which are to receive the indicia. Often, contact between the printing device and the articles is beneficial in assuring that proper markings are transferred to the articles, and that the articles are maintained in proper position during this procedure. For example, direct contact between the printing device and the articles is often important in assuring that a sharp image is transferred to the product. In many cases, direct contact between the printing device and the articles is essential to such a transfer. This would particularly apply to the spin-printing of capsules, caplets and the like, since contact between the printing device and the articles which are to receive the indicia must be sufficient to cause the articles to spin within an appropriate carrier so that the desired indicia are properly applied about the circumference of the articles.
However, in some cases, the articles which are to receive the indicia have been found to be so fragile that a certain potential for breakage of the articles may arise in the course of the printing procedure. This problem most clearly manifests itself in the application of indicia to candies and the like, although similar problems may also be encountered in connection with certain pharmaceutical formulations, depending upon their consistencies. The contact pressure which is applied against such articles may be adjusted (reduced) in an effort to overcome this problem. However, this too presents a problem in that the resiliency of the printing roll tends to vary in use, causing changes over time. Moreover, this reduction in potential for breakage is achieved at the expense of less reliable printing, since contact between the printing device and the articles is reduced.
Such difficulties can result either in the incomplete application of indicia (partially or entirely) to the articles, at one extreme, or damage to the articles, at the other. These problems are further complicated when irregularly shaped pellets are to be marked, since the surface characteristics of such articles cannot be predicted, making the necessary penetration of the contacting printing device even more difficult to establish.
It therefore became desirable to develop an alternative to contact-type printing devices to enable the application of indicia to pellets which are unable to satisfactorily withstand the constraints of actual contact with the printing device.